Resin extractor for additive manufacturing

ABSTRACT

A method of separating excess resin (15) from at least one object (11), includes: (a) stereolithographically producing at least one object (11) on at least one carrier platform (10), each carrier platform (10) having a planar build surface to which at least one object (11) is connected, each object (11) carrying excess resin (15) on a surface thereof; then (b) mounting each carrier platform (10) to a rotor (31); (c) centrifugally separating excess resin (15) from each object (11) by spinning the rotor (31) with each carrier platform (10) connected thereto while each object (11) remains connected to each carrier platform (10); and then (d) removing each carrier platform (10) from the rotor (31) with each object (11) thereon, with excess resin (15) separated therefrom.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplications Ser. Nos. 62/661,421, filed Apr. 23, 2018, and 62/772,858,filed Nov. 29, 2018, the disclosures of which are incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The present invention concerns methods of additive manufacturing, andparticularly concerns methods of extracting or removing excess resinfrom objects following their production by top-down or bottom-upstereolithography.

BACKGROUND OF THE INVENTION

A group of additive manufacturing techniques sometimes referred to as“stereolithography” create a three-dimensional object by the sequentialpolymerization of a light polymerizable resin. Such techniques may be“bottom-up” techniques, where light is projected into the resin onto thebottom of the growing object through a light transmissive window, or“top down” techniques, where light is projected onto the resin on top ofthe growing object, which is then immersed downward into a pool ofresin.

The recent introduction of a more rapid stereolithography techniquesometimes referred to as continuous liquid interface production (CLIP)has expanded the usefulness of stereolithography from prototyping tomanufacturing. See J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al.,Continuous liquid interface production of 3D objects, SCIENCE 347,1349-1352 (published online 16 Mar. 2015); U.S. Pat. Nos. 9,211,678;9,205,601; and 9,216,546 to DeSimone et al.; see also R. Janusziewicz,et al., Layerless fabrication with continuous liquid interfaceproduction, PNAS 113, 11703-11708 (18 Oct. 2016).

Dual cure resins for additive manufacturing were introduced shortlyafter the introduction of CLIP, expanding the usefulness ofstereolithography for manufacturing a broad variety of objects stillfurther. See Rolland et al., U.S. Pat. Nos. 9,676,963, 9,453,142 and9,598,606; J. Poelma and J. Rolland, Rethinking digital manufacturingwith polymers, SCIENCE 358, 1384-1385 (15 Dec. 2017).

Stereolithography resins—both conventional and dual cure—are generallyviscous, and excess, unpolymerized, resins adhere to objects after theyhave been produced. Various wash techniques for removing excess resinare known (see, for example, W. McCall et al., Wash liquids for use inadditive manufacturing with dual cure resins, US Patent Application Pub.No. 2017/0173872), but such techniques are generally slow, are notadapted for high through-put manufacturing situations, may require largeamounts of wash liquids, and—because the excess resin is carried away inthe wash liquid—generally preclude collection and use of the excessresin in subsequent stereolithographic production steps. Accordingly,there is a need for new techniques for removing excess resin fromadditively manufactured products.

SUMMARY OF THE INVENTION

A method of separating excess resin from at least one object includesthe steps of: (a) stereolithographically producing at least one object(e.g., two, three or more) on at least one carrier platform (e.g., two,three, four or more), each carrier platform having a planar buildsurface to which the object(s) is/are connected, each object carryingexcess resin on a surface thereof; then (b) mounting each carrierplatform to a rotor; (c) centrifugally separating excess resin from eachobject by spinning the rotor with each carrier platform connectedthereto, while each object remains connected to its correspondingcarrier platform; and then (d) removing each carrier platform from therotor with its corresponding object(s) remaining thereon, but withexcess resin separated therefrom.

In some embodiments, the centrifugally separating step is carried outwith each carrier platform mounted to the rotor with the build surfaceoriented perpendicularly to a radius of the rotor and tangentially to anaxis of rotation of said rotor.

In some embodiments, the method includes warming the excess resinsufficiently to reduce the viscosity thereof during the centrifugallyseparating step.

In some embodiments, the method includes applying a solvent (e.g., byspraying) to the excess resin in an amount sufficient to reduce theviscosity thereof during the centrifugally separating step.

In some embodiments, the centrifugally separating step is carried out ina gas (e.g., air, an inert gas) at ambient pressure or a pressure lessthan ambient pressure.

In some embodiments, the rotor includes a primary rotor and a pluralityof secondary rotors mounted on the primary rotor, wherein each carrierplatform is mounted on one of the secondary rotors, and wherein thespinning step is carried out by rotating the primary rotor whilerotating (e.g., counter-rotating) the secondary rotors.

In some embodiments, the method can further include the steps of: (e)collecting the centrifugally separated excess resin, then (f) optionallycombining the excess resin with additional resin; and then (g)stereolithographically producing at least one additional object from thecollected (and optionally diluted) excess resin.

In some embodiments, the object includes an intermediate object producedfrom a dual cure resin, the method can further include the steps of: (h)optionally separating each the object from each the carrier platform;and then (i) further curing (e.g., by heating and/or microwaveirradiating) the object to produce a finished object.

In some embodiments, the object comprises (in whole or in part) an openlattice structure. In some embodiments, the object includes one or moreinternal cavities, has at least one opening formed therein in fluidcommunication the cavity, the opening configured for excess resin withinthe cavity to flow therethrough and out of the cavity during thecentrifugally separating step. In some embodiments, the object comprisesa dental model or die.

In some embodiments, the object(s) on each carrier platform have ahigher drag orientation and a lower drag orientation, and thecentrifugally separating step is carried out with the carrierplatform(s) mounted on the rotor with the object(s) positioned in thelower-drag orientation.

In some embodiments, the object(s) has or have a long dimension, and theobject(s) is or are oriented on the carrier platform with the longdimension substantially parallel to the planar build surface (e.g., plusor minus 20 or 30 degrees).

In some embodiments, the method includes measuring at least onecharacteristic or parameter associated with each carrier platform usingat least one force gauge that engages or interfaces with the at leastone carrier platform. In some embodiments, the characteristic orparameter includes the amount of resin separated from each object on theat least one carrier platform and/or the amount of resin remaining oneach object on the at least one carrier platform (e.g., during thecentrifugally separating step).

A further aspect of the present invention is a centrifugal extractorapparatus configured for carrying out a method as described above, andin further detail below.

For example, an apparatus for separating excess resin from at least oneobject, includes: a collection vessel; and a rotor in the collectionvessel and configured to receive at least one carrier platform having atleast one object thereon and to spin with each carrier platformconnected thereto such that excess resin from each object is removed andoptionally received in the collection vessel.

In some embodiments, the collection vessel is sealable. The apparatusmay further include a vacuum line connected to the collection vessel andconfigured to reduce pressure in the collection vessel to reduce drag oneach object as it is spun by the rotor.

In some embodiments, the apparatus includes a resin drain line connectedto the collection vessel and configured to collect the excess resin forrecycling in a subsequent stereolithographic production process.

In some embodiments, the apparatus includes at least one force gaugethat engages the at least one carrier platform, with each force gaugeconfigured to measure at least one characteristic or parameterassociated with the carrier platform to which it is engaged. In someembodiments, the at least one characteristic or parameter includes theamount of resin separated from each object on the carrier platformand/or the amount of resin remaining on each object on the carrierplatform.

The foregoing and other objects and aspects of the present invention areexplained in greater detail in the drawings herein and the specificationset forth below. The disclosures of all United States patent referencescited herein are to be incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates one embodiment of stereolithography, inwhich excess resin is carried on the surface of the object beingproduced.

FIG. 2 schematically illustrates one embodiment of a method andapparatus for extracting resins from stereolithographically producedobjects.

FIG. 3 is a top plan view of a portion of the method and apparatus ofFIG. 2.

FIG. 4 schematically illustrates a further non-limiting embodiment of anapparatus of the present invention.

FIG. 5 is a top plan view of a portion of a method and apparatus similarto FIG. 2, except now showing alternate orientations of objects thereon.

FIG. 6 is a schematic top plan view of another embodiment of the presentinvention, in which a compound rotor is implemented.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

1. Stereolithography Apparatus and Resins.

Resins for additive manufacturing are known and described in, forexample, DeSimone et al., U.S. Pat. Nos. 9,211,678; 9,205,601; and9,216,546. Dual cure resins for additive manufacturing are known anddescribed in, for example, Rolland et al., U.S. Pat. Nos. 9,676,963;9,598,606; and 9,453,142. Non-limiting examples of dual cure resinsinclude, but are not limited to, resins for producing objects comprisedof polymers such as polyurethane, polyurea, and copolymers thereof;objects comprised of epoxy; objects comprised of cyanate ester; objectscomprised of silicone, etc.

Techniques for additive manufacturing are known. Suitable techniquesinclude bottom-up or top-down additive manufacturing, generally known asstereolithography. Such methods are known and described in, for example,U.S. Pat. No. 5,236,637 to Hull, U.S. Pat. Nos. 5,391,072 and 5,529,473to Lawton, U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 toShkolnik, U.S. Pat. No. 8,110,135 to El-Siblani, U.S. Patent ApplicationPublication No. 2013/0292862 to Joyce, US Patent Application PublicationNo. 2013/0295212 to Chen et al, and U.S. Patent Application PublicationNo. 2018/0290374 to Willis and Adzima. The disclosures of these patentsand applications are incorporated by reference herein in their entirety.

FIG. 1 schematically illustrates one embodiment of stereolithographicproduction (in this case a bottom-up technique). A carrier platform 10carries the object being produced, which is above a light-transmissivewindow 12. A light source, such as a UV light source 13, projectsspatially and temporally patterned light through the window 12 intoresin 15 resting on top of the window, while the carrier platform 10 andwindow 12 are advanced away from one, typically another, in the zdirection (for example, by means of an elevator mechanism 14 to whichthe carrier platform 10 is connected). Note resin 15 adhered to thesurface of object 11 as well as on top of window 12.

In some embodiments, the object is formed by continuous liquid interfaceproduction (CLIP). CLIP is known and described in, for example, PCTApplication Nos. PCT/US2014/015486 (U.S. Pat. No. 9,211,678);PCT/US2014/015506 (U.S. Pat. No. 9,205,601), PCT/US2014/015497 (U.S.Pat. No. 9,216,546), and in J. Tumbleston, D. Shirvanyants, N. Ermoshkinet al., Continuous liquid interface production of 3D Objects, Science347, 1349-1352 (2015). See also R. Janusziewcz et al., Layerlessfabrication with continuous liquid interface production, Proc. Natl.Acad. Sci. USA 113, 11703-11708 (Oct. 18, 2016). In some embodiments,CLIP employs features of a bottom-up three-dimensional fabrication asdescribed above, but the irradiating and/or said advancing steps arecarried out while also concurrently maintaining a stable or persistentliquid interface between the growing object and the build surface orwindow, such as by: (i) continuously maintaining a dead zone ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone (such as anactive surface) between the dead zone and the solid polymer and incontact with each thereof, the gradient of polymerization zonecomprising the first component in partially-cured form. In someembodiments of CLIP, the optically transparent member comprises asemipermeable member (e.g., a fluoropolymer), and the continuouslymaintaining a dead zone is carried out by feeding an inhibitor ofpolymerization through the optically transparent member, therebycreating a gradient of inhibitor in the dead zone and optionally in atleast a portion of the gradient of polymerization zone. Other approachesfor carrying out CLIP that can be used in the present invention andobviate the need for a semipermeable “window” or window structureinclude utilizing a liquid interface comprising an immiscible liquid(see L. Robeson et al., WO 2015/164234, published Oct. 29, 2015),generating oxygen as an inhibitor by electrolysis (see I Craven et al.,WO 2016/133759, published Aug. 25, 2016), and incorporating magneticallypositionable particles to which the photoactivator is coupled into thepolymerizable liquid (see J. Rolland, WO 2016/145182, published Sep. 15,2016). See also U.S. Patent Application Publication No. 2018/0243976 toFeller; U.S. Patent Application Publication No. 2018/0126630 to Panzerand Tumbleston; and U.S. Patent Application Publication No. 2018/0290374to Willis and Adzima.

Other examples of methods and apparatus for carrying out particularembodiments of CLIP include, but are not limited to: Batchelder et al.,Continuous liquid interface production system with viscosity pump, USPatent Application Pub. No. US 2017/0129169 (May 11, 2017); Sun andLichkus, Three-dimensional fabricating system for rapidly producingobjects, US Patent Application Pub. No. US 2016/0288376 (Oct. 6, 2016);Willis et al., 3d print adhesion reduction during cure process, USPatent Application Pub. No. US 2015/0360419 (Dec. 17, 2015); Lin et al.,Intelligent 3d printing through optimization of 3d print parameters, USPatent Application Pub. No. US 2015/0331402 (Nov. 19, 2015); and D.Castanon, Stereolithography System, US Patent Application Pub. No. US2017/0129167 (May 11, 2017).

In the embodiment of FIG. 1 the liquid interface 16 is shown, but in thepresent invention CLIP is not required, and top-down stereolithographymay be used as well as bottom-up stereolithography.

After the object is formed, it is typically cleaned, and then furthercured, preferably by baking (although further curing may in someembodiments be concurrent with the first cure, or may be by differentmechanisms such as contacting to water, as described in U.S. Pat. No.9,453,142 to Rolland et al.).

2. Resin Extractor Apparatus and Methods.

FIGS. 2-3 schematically illustrate non-limiting embodiments of a methodand apparatus of the present invention. The apparatus comprises a rotor31 having at least one or a plurality of mounts 32 to which carrierplatform(s) 10 may be removably secured. The resulting assembly canoptionally, but preferably, be contained in a collection vessel 33. Theplatforms have stereolithographically produced object(s) 11 thereon,which are coated with excess resin 15. Upon rotation of therotor/mount/platform/object assembly, resin is centrifugally spun off ofthe objects 11, where it may be collected in the collection vessel 33.The carrier platforms 10 are preferably aligned perpendicularly to therotor, and the carrier platforms can have planar top surfaces which arealigned tangentially to the rotor axis of rotation b (see FIG. 3). Themounts 32 may extend perpendicular to the the rotor axis of rotation band the build surfaces of the carrier platforms 10 may be parallel tothe rotor axis of rotation b.

The rotor 31 can be driven by any suitable drive mechanism (not shown)including but not limited to electric, pneumatic, and hydraulic drives.The rotor may be spun at any suitable speed, and in some embodiments isspun at a maximum speed between 100, 200 or 400 revolutions per minute(rpm) to 1,000, 1,200, or 2,000 rpm, or more. There are preferablyperiods of acceleration and deceleration at the beginning and end ofeach centrifugally separating step before maximum speed is achieved, andthe choice of maximum speed will depend on factors such as overallduration of the centrifugally separating step (with longer durationsallowing for lower speeds), viscosity of excess resin, temperature,geometry of the object(s), any use of warming or solvents (discussedbelow), the amount of drag or wind the objects can withstand withoutdamage, the resonant frequencies of the objects or the apparatus, etc.In some embodiments, the duration of the centrifugally separating stepcan be from 20 or 40 seconds to 2, 5 or 10 minutes, or more.Centrifugally separating steps can optionally be repeated, and stepsbetween such repeats (such as a solvent dunk or spray) may be introducedif desired.

Automatic balancers (not shown) can be operatively associated with therotors, such as those described in, for example, U.S. Pat. No. 2,584,942to Thearle; U.S. Pat. No. 4,157,781 to Maruyama; U.S. Pat. No. 5,376,063to Greenstein; U.S. Pat. No. 5,862,553 to Haberl; and U.S. Pat. No.6,578,225 to Jonsson, the disclosures of which are incorporated hereinby reference. In another embodiment, the mount(s) 32 may be radiallyadjustable to manually balance the rotor 31 once carrier platform(s) 10and their corresponding object(s) 11 are mounted thereto.

Referring to FIG. 3, the apparatus may include one or more force gauges39. For example, the force gauges 39 may be on the mounts 32. The forcegauges 39 may be operatively associated with a controller and used for:determining the amount of resin removed and/or the amount of resinremaining (e.g., on each object); closed-loop determinations of idealspin cycles; determining appropriate spin program and part removaladjustments; predictive fault management (e.g., determine if somethinghas broken or changed that could be a hazard); and/or detecting if acarrier platform is present (e.g., connected to the rotor) and is thecorrect weight. The force gauges 39 may be single point, compression, orplanar beam type load cells. Each force gauge 39 may engage or interfacewith the restrained portion of one or the carrier platforms 10.

A further embodiment, schematically illustrated in FIG. 4, shows variousadditional steps and features that may be included in some embodimentsof the methods and apparatus of the present invention. The collectionvessel can be provided with a hood, lid, or access door, and appropriateseal, so that the pressure therein may be reduced below ambient pressurevia a vacuum line 34, sufficiently to reduce drag on the objects as theyare spun in the gas atmosphere. The separating step can be carried outin a gas, typically air at ambient pressure, but a supply line (notshown) for an inert gas such as argon, nitrogen, or carbon dioxide canbe included, if a resin and/or solvent is volatile or flammable. Heaters(e.g., infrared heaters) 35 may be included to warm the objects and theexcess resin, sufficiently to reduce the viscosity thereof during thecentrifugally separating step (and thereby reducing the maximum speed atwhich rotation is carried out, and/or the duration of the centrifugallyseparating step). Spray nozzles 36 may be included to apply a solventsuch as isopropanol to the excess resin, in an amount sufficient toreduce the viscosity thereof during the centrifugally separating step,and again reduce the maximum speed or duration of the separating step.Air blades or air jets may be included in addition to, or instead of,such spray nozzles, again to aid in removal of excess resin from theobjects. A resin drain line 37 can be included to facilitate collectionof resin, such as when resin is to be recycled to a subsequentstereolithographic production step, and flow actuators 38 (such asshakers, vibrators, ultrasonic vibrators, etc.) can be provided inoperative association with the collection vessel to encourage flow ofthe collected, viscous, resin. One or more of these features may beuseful for the production of objects that are dental models and/or dies,which may be formed by photopolymerizing a viscous resin. The collectionvessel may include a removable liner (not shown), such as a rigid orflexible polymer liner, to aid in cleaning the vessel, and/or incollecting excess resin. Similarly, the objects may be wrapped orcovered with a removable cover (not shown) such as a rigid or flexiblepolymer wrap or cover, to aid in collection of excess resin in a morelocalized fashion.

As shown in FIG. 5, in some embodiments the object(s) 11 has or have along dimension, and in some embodiments those objects may be oriented onthe carrier platform 10 with the long dimension substantially parallelto the planar build surface (e.g., plus or minus 20 or 30 degrees). Inother embodiments, however, it may be desired to have the object(s) longdimension substantially perpendicular to the carrier platform (e.g.,plus or minus 20 or 30 degrees), such as where many objects are carriedby the same carrier platform in a “high density” production thereof Asalso illustrated in FIG. 5, depending on the direction of rotationduring centrifugation, objects 11, 11′ will have a variety ofhigher-drag orientations, and a variety of lower-drag orientations, onthe platform 10. In some embodiments, it will be preferable to orientthe object (e.g., during its stereolithographic production, or bymanipulation of the platform on the mount 32) so that it is positionedon the rotor in a lower-drag orientation. Note that, in theseembodiments, it may not be necessary to position the object in itslowest drag orientation, as other considerations (such as balance,printability during additive production, etc.) may weigh against thatpositioning. In addition, if desired, aerodynamic baffles (not shown)may be included on the rotor, or attachable to the rotor and/or thecarrier platforms, to shield the objects from excess wind load or dragduring rotation. Similarly, if desired, the mount may be a rotatablemount, able to rotate about an axis normal to the build surface (e.g.,the platform's (and object's) Z axis), and then lock in place, toprovide advantageous positioning of the object for reducing wind load ordrag.

In the embodiment schematically illustrated in FIG. 6, the rotor is acompound rotor comprised of a primary rotor 31 a and a plurality ofsecondary rotors 31 b mounted on the primary rotor. One, two, three ormore carrier platforms 10 can be mounted on each secondary rotor 31 b inlike manner as described above, and the spinning step is carried out byrotating the primary rotor 31 a while counter-rotating the secondaryrotors 31 b, thereby subjecting the carrier platforms to compoundrotation. The primary and secondary rotors may be driven by any suitabledrive mechanism, including but not limited to those set forth in U.S.Pat. No. 3,013,365 to Harper; U.S. Pat. No. 4,776,135 to Thum; or U.S.Pat. No. 5,355,638 to Hoffman, the disclosures of which are incorporatedherein by reference.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

1. A method of separating excess resin from at least one object,comprising: (a) stereolithographically producing at least one object onat least one carrier platform using an elevator mechanism to advanceeach carrier platform away from a window, each said carrier platformhaving a planar build surface to which at least one object is connected,each said object carrying excess resin on a surface thereof; then (b)mounting each said carrier platform to a rotor; (c) centrifugallyseparating excess resin from each said object by spinning said rotorwith each said carrier platform connected thereto while each said objectremains connected to each said carrier platform; and then (d) removingeach said carrier platform from said rotor with each said objectthereon, with excess resin separated therefrom, wherein saidcentrifugally separating step is carried out with each said carrierplatform mounted to said rotor with said build surface oriented parallelto an axis of rotation of said rotor.
 2. The method of claim 1, whereinsaid centrifugally separating step is carried out with each said carrierplatform mounted to said rotor with said build surface orientedperpendicularly to a radius of the rotor and tangentially to said axisof rotation of said rotor.
 3. The method of claim 1, wherein said atleast one carrier platform comprises at least two or three carrierplatforms.
 4. The method of claim 1, wherein each said carrier platformhas at least two or three stereolithographically produced objectsconnected thereto.
 5. The method of claim 1, further comprising warmingsaid excess resin sufficiently to reduce the viscosity thereof duringsaid centrifugally separating step.
 6. The method of claim 1, furthercomprising applying a solvent to said excess resin in an amountsufficient to reduce the viscosity thereof during said centrifugallyseparating step.
 7. The method of claim 1, wherein said centrifugallyseparating step is carried out in a gas at ambient pressure or apressure less than ambient pressure.
 8. The method of claim 1, whereinsaid rotor comprises a primary rotor and a plurality of secondary rotorsmounted on said primary rotor, wherein each said carrier platform ismounted on one of said secondary rotors, and wherein said spinning stepis carried out by rotating said primary rotor while rotating saidsecondary rotors.
 9. The method of claim 1, wherein said spinning iscarried out at a speed of from 200 or 400 revolutions per minute (rpm)to 1,000 or 1,2000 rpm, or more.
 10. The method of claim 1, furthercomprising: (e) collecting said centrifugally separated excess resin,then (f) optionally combining said centrifugally separated excess resinwith additional resin; and then (g) stereolithographically producing atleast one additional object from said centrifugally separated excessresin and/or said additional resin.
 11. The method of claim 1, whereinsaid object comprises an intermediate object produced from a dual cureresin, the method further comprising: (h) optionally separating eachsaid object from each said carrier platform; and then (i) further curingsaid object to produce a finished object.
 12. The method of claim 1,wherein said object comprises a lattice and/or includes one or moreinternal cavities and has at least one opening formed therein in fluidcommunication with the cavity and configured for excess resin within thecavity to flow therethrough and out of the cavity during thecentrifugally separating step.
 13. The method of claim 1, wherein saidobject(s) on each said carrier platform have a higher drag orientationand a lower drag orientation, and said centrifugally separating step iscarried out with said carrier platform(s) mounted on said rotor withsaid object(s) positioned in said lower-drag orientation.
 14. The methodof claim 1, wherein said object(s) has or have a long dimension, andsaid object(s) is or are oriented on said carrier platform with saidlong dimension substantially parallel to said planar build surface. 15.The method of claim 1 further comprising measuring at least onecharacteristic or parameter associated with each said carrier platformusing at least one force gauge that engages or interfaces with said atleast one carrier platform.
 16. The method of claim 15 wherein saidcharacteristic or parameter comprises the amount of resin separated fromeach object on said at least one carrier platform and/or the amount ofresin remaining on each object on said at least one carrier platform.17. The method of claim 1 further comprising removing each said carrierplatform from the elevator mechanism before mounting each said carrierplatform to the rotor.
 18. A centrifugal extractor configured forcarrying out the method of claim
 1. 19. An apparatus configured forcarrying out the method of claim
 1. 20. An apparatus for separatingexcess resin from at least one object, comprising: a collection vessel;and a rotor in the collection vessel and configured to receive at leastone carrier platform having at least one object thereon and to spin witheach carrier platform connected thereto such that excess resin from eachobject is removed and optionally received in the collection vessel,wherein each said carrier platform comprises a planar build surface towhich said at least one object is connected, and said rotor isconfigured to receive each said carrier platform with said build surfaceoriented parallel to an axis of rotation of said rotor.
 21. Theapparatus of claim 20, wherein the collection vessel is sealable, andwherein the apparatus further comprises a vacuum line connected to thecollection vessel and configured to reduce pressure in the collectionvessel to reduce drag on each object as it is spun by the rotor.
 22. Theapparatus of claim 20, further comprising a resin drain line connectedto the collection vessel and configured to collect the excess resin forrecycling in a subsequent stereolithographic production process.
 23. Theapparatus of claim 20, further comprising at least one force gauge thatengages the at least one carrier platform, each force gauge configuredto measure at least one characteristic or parameter associated with thecarrier platform to which it is engaged.
 24. The apparatus of claim 23,wherein the at least one characteristic or parameter comprises theamount of resin separated from each object on the carrier platformand/or the amount of resin remaining on each object on the carrierplatform.